Ethynylthiophenoxy derivatives of diphenylhexafluoropropane

ABSTRACT

Ethynylphenyl derivatives of diphenylhexafluoropropane having the formula: ##STR1## where X is oxygen or sulfur and each of R, R 1 , or R 2  is hydrogen or ethynyl. The compounds are useful in forming polymer structures, either homopolymers or copolymers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to diethynylated aromaticcompounds. More particularly, the present invention relates todiphenylhexafluoropropane compounds having an ethynylphenoxy orethynylthiophenoxy group attached to the phenyl rings of thediphenylhexafluoropropane.

2. Description of the Background Art

Diethynylated aromatic compounds are important intermediates in thesynthesis of thermally stable resins for use in high-temperaturestructural composites, and high-char yielding structure matrices, suchas carbon-carbon composites. These materials are used in the fabricationof reentry missile nose cones, leading edges, rocket nozzles, and otherstructural applications requiring high structural strength and highthermal stability.

The processing and fabrication of these high temperature resins isgenerally rather difficult. When using the diethynylated aromaticcompounds by themselves or as diluents in various high temperatureresins and composite products, it is important that the compound be in afluid state over a relatively large workable temperature range in orderto facilitate processing. This workable or fluid temperature range isgenerally referred to as the "processing window" for the givendiethynylated aromatic compound. The lower limit of the processingwindow is the temperature at which the compound melts to a liquid state,while the upper limit is the temperature at which the compound gels andsolidifies. If possible, it is desirable to use compounds which haveprocessing windows encompassing ambient temperatures in order tosimplify resin fabrication and make the process commercially practical.

There are presently only two known diethynylated aromatic compoundswhich are viscous liquids at ambient temperatures. One is anacetylene-terminated sulfone (ATS) and the other is2,2-bis(4-ethynylphenyl) hexafluoropropane (EPHFP). EPHFP and relatedcompounds are disclosed in U.S. Pat. No. 4,374,291 which issued Feb. 15,1983, to the same assignee as the present invention. It would bedesirable to provide additional diethynylated aromatic compounds whichhave processing windows in the same range as the above discussed knowncompounds and which also provide additional properties andcharacteristics not found in either of the two known compounds.

SUMMARY OF THE INVENTION

In accordance with the present invention, new diethynylated aromaticcompounds are disclosed which have a large processing window whichextends from 71° C. to 225° C. The new compounds cure to yieldcross-linked networks that are more highly thermally stable than theknown ATS or EPHFP compounds and which have higher glass transitiontemperatures.

The compounds in accordance with the present invention areethynylphenoxy and ethynylthiophenoxy derivatives ofdiphenylhexafluoropropane which have the following formula: ##STR2##where X is oxygen or sulfur and each of R, R₁, or R₂ is hydrogen orethynyl. In the preferred compositions, R₁ and R₂ are hydrogen and R isethynyl.

The large processing window of the new compounds allows easy handlingand blending with other high temperature oligomers and polymers, thusacting as a compatible diluent to improve processing of the hightemperature polymer materials which are otherwise difficult to process.(The term compatibility is generally referred to herein to mean theavoidance of phase separation of the blended polymers in the resinmixture.) In addition, blending and copolymerization of the newcompounds with other acetylene-terminated oligomers yieldsinterpenetrating copolymer networks that are suitable structuralmaterials for high temperature applications.

The compounds of the present invention are also useful as plasticizingdiluents for use in processing high molecular weight thermoplastics.Curing of high molecular weight thermoplastics with the compounds of thepresent invention incorporated therein produces a cross-linked networkwithin the thermoplastic to enhance the high temperature structuralstrength of the thermoplastic.

As another feature of the present invention, the presence of flexibleoxygen or sulfur linkages (X) between the hexafluoroisopropylidenegroups and the ethynylphenyl groups, along with the large moleculardistance between the ethynyl end groups yields polymers and copolymershaving improved resistance to fracturing.

The above-discussed and many other features and attendant advantages ofthe present invention will become apparent as the invention becomesbetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of two alternate exemplaryprocesses for preparing a preferred ethynylphenoxy derivative ofdiphenylhexafluoropropane in accordance with the present invention.

FIG. 2 is a schematic representation of an exemplary process forpreparing a preferred ethynylthiophenoxy derivative ofdiphenylhexafluoropropane in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Compounds in accordance with the present invention have the generalformula: ##STR3## where X is oxygen or sulfur and each of R, R₁ or R₂ ishydrogen or ethynyl. A preferred compound is2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane where X is oxygen,R₁ and R₂ are hydrogen and R is ethynyl. Another preferred compound is2,2-bis[4-(4-ethynylphenylthio)phenyl]hexafluoropropane where X issulfur, R₁ and R₂ are hydrogen and R is ethynyl. Exemplary preparationof these two preferred embodiments are as follows.

The preparation of 2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane(5) is shown schematically in FIG. 1. The2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane (5) can be made bytwo preferred synthesis routes. Each route involves preparation of2,2-bis[4-(4-iodophenoxy)phenyl]hexafluoropropane (2) followed byreaction with either 2-methyl-3-butyn-2-ol or ethynyltrimethysilane toproduce the intermediates (3) and (4) respectively as shown in FIG. 1.Each of the two intermediates is then treated as discussed below to formthe desired 2,2-bis[4-(4-ethynylphenoxy)phenyl]hexa-fluoropropane (5).

Examples of practice are as follows.

EXAMPLE 1

This example illustrates the preparation of2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane (5) in accordancewith the present invention.

A. Preparation of 2,2-Bis[4-(4-iodophenoxy)phenyl]hexafluoropropane(Compound 2)

2,2-Bis[4-(4-iodophenoxy)phenyl]hexafluoropropane (Compound 2) wasprepared by first placing 250 ml of concentrated hydrochloric acid in a4-liter beaker. While being stirred mechanically, the acid was treatedwith 103.6 grams (0.2 mole) of2,2-bis[4-(4-aminophenoxy)-phenyl]hexafluoropropane (1) (available fromMorto Chemical Company as 4-BDAF). To this slurry was added 400 grams ofice to give a final temperature of -15° C. By drop-by-drop addition, a500 ml aqueous solution of 30.4 grams (0.44 mole) of sodium nitrite wasadded. As heat was generated, the reaction mixture must be controlled ata temperature range of -5° C. to 0° C. by the addition of ice. At theend, the slurry changed to a reddish brown solution which turned KIstarch paper blue. The solution was stirred for an additional 0.5 hr at0° C. A solution of 73 grams (0.44 mole) of potassium iodide in 250 mlof water was added at such a rate that foaming was under control. Afterthe addition of potassium iodide, the mixture was allowed to stand at25° C. for 16 hrs.

The solution was neutralized and extracted in several portions with atotal of 2 liters of dichloromethane. The organic phase was washed with3×500 ml of aqueous sodium bisulfite, 1×500 ml of aqueous sodiumbicarbonate and 2×500 ml of water. After drying over magnesium sulfateand concentrating, 121.9 grams of a brown solid was obtained and waspurified by silica gel column chromatography using 1:10dichloromethane-hexane as eluant. At the end, 70.4 grams of acreamy-white solid was obtained: M.P. 128°-131° C.

A second silica gel column chromatography on a 1 gram sample of theproduct noted immediately above afforded lustrous white rhombic crystalsof 2,2-bis[4-(4-iodophenoxy)phenyl]hexafluoropropane (2) which wasmelted at 140°-141° C.

The physical properties for the compound (2) are:

IR (KBr): 3170 (weak), 1620, 1585, 1515, 1485, and very strongabsorption at 1300-1175 cm⁻¹ ;

NMR (CDCl₃): δ6.74-7.80 ppm (2 overlapping distorted AB splittingpatterns.)

B. Preparation of2,2-Bis[4-[4-(3-hydroxy-3-methylbut-1-ynyl)phenoxy]phenyl]hexafluoropropane(Compound 3)

To a solution of 59.2 grams (0.08 mole) of Compound 2 in 300 ml ofdeaerated anhydrous triethylamine (Fluka), were added 250 mg of (Ph₃ P)₂PdCl₂, as the precursor for zero valent palladium. The mixture washeated at approximately 45° C. with stirring until all particles haddissolved. As one portion, 14.8 g (0.176 mole) of 2-methyl-3-butyn-2-olwas added followed by 68.5 mg of Cu₂ I₂. The temperature of the oil bathwas raised to about 95°-100° C. and maintained in this range for 4.5hrs. After cooling and diluting with 300 ml of ether, the slurry wasfiltered to yield 34.07 g of triethylamine hydroiodide (0.149 mole, 93%of theory).

The filtrate was concentrated to dryness, redissolved in 200 ml ofdichloromethane and washed with 100 ml each of 10% hydrochloric acid,water, saturated sodium bicarbonate and water again. After drying overmagnesium sulfate and concentrating, the residue was purified by silicagel column chromatography. Elution with hexane removed the diacetyleneside product. Eluting with acetone and concentrating the eluate yieldeda tan solid (51.9 g, 0.080 mole, 99.5% of theory) which was identifiedas Compound 3. Compound 3 had the following properties: M.P. 73°-77° C.;IR (film): 3400 (broad, strong OH), 3000 (sharp, strong methyl), 2240(weak, C--C), 1600, 1505, and 1300-1140 cm⁻¹ (strong, broad); NMR(acetone-d₆): δ1.05 (s,12 H,CH₃), 6.40-7.05 ppm (2 overlapping A₂ B₂quartets, 16 H, aromatic H's).

Analysis for C₃₇ H₃₀ F₆ O₄ (444.407):

Calculated: C, 68.09; H, 4.63.

Found: C, 68.17; H, 4.89.

C. Preparation of 2,2-Bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane(Compound 5) from2,2-[4-[4-(3-Hydroxy-3-methylbut-1-ynyl)phenoxy]phenyl]hexafluoropropane(Compound 3)

A solution of 0.32 grams (0.008 mole) of sodium hydroxide in 5 ml ofwater was added to 31.9 grams (0.050 mole) of Compound 3 in 150 ml oftoluene. After refluxing for 2 hours, the mixture was thenazeotropically distilled. The cloudy liquid that distilled containedacetone.

After cooling, the mixture was washed with 100 ml of water, dried overmagnesium sulfate, and concentrated to a solid mass. The solid mass waspurified by column chromatography eluting with hexane. The pale yellowsolid was identified as2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane (Compound 5) by thecharacteristic 2210 cm⁻¹ absorption in its IR spectrum and also by thedistinctive singlet at δ3.14 ppm and a distorted AB pattern atδ6.90-7.85 ppm in its NMR spectrum.

D. Preparation of2,2-Bis[4-(4-trimethylsilylethynylphenoxy)phenyl]hexafluoropropane(Compound 4)

To a solution of 26.45 grams (35.74 mmoles) of Compound 2, prepared asnoted above, in 200 ml of deaerated, anhydrous triethylamine, was addedthe catalyst system which comprised 48 mg of palladium[II]acetate and200 mg of triphenylphosphine, and which provides, upon reduction, zerovalent palladium. The cloudy yellow solution was stirred and heated at50° C. until all of the brown particles dissolved.Ethynyltrimethylsilane (8.760 g, 89.39 mmoles) was added and the mixturewas rapidly heated to 70° C. over 5 minutes. At 60° C., a clear yellowsolution was obtained. At 70° C., precipitation of the whitetriethylamine hydroiodide commenced. The reaction temperature was raisedto 90°-95° C. over 10 minutes and maintained at that temperature rangefor 6 hours. After one hour, an unexpected decomposition of thepalladium complex took place and the white precipitate took on a greycolor. The slurry was then cooled, diluted with 100 ml of ether andfiltered. The grey solid was washed with more ether and air-dried. Avirtually quantitative yield (15.64 g, 71.42 mmoles) of triethylaminehydroiodide was realized.

The dark brown filtrate was concentrated, dissolved in 200 ml of etherand washed with 100 ml each of 10% hydrochloric acid, water, saturatedsodium bicarbonate adn water again. The ethereal phase was dried overmagnesium sulfate and concentrated to a foamy semisolid. The crude yieldwas virtually quantitative. A one-gram sample was removed and waspurified by column chromatography. The second band travelled down thecolumn was eluted with 1.5 liters of hexane. The eluate was concentratedto a molasses consistency to provide a light yellow semi-solid2,2-bis[4-(4-trimethylsilylethynylphenoxy)phenyl]hexafluoropropane(Compound 4).

E. Alternative Preparation of2,2-Bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane (Compound 5) from2,2-Bis-[4-(4-trimethylsilylethynylphenoxy)phenyl]hexafluoropropane(Compound 4)

The light yellow semi-solid (Compound 4) obtained immediately above wasdissolved in 200 ml of a mixture of 1:1 anhydrousmethanol-tetrahydrofuran and stirred with 2 grams of anhydrous potassiumcarbonate at 25° C. for 16 hours. The solution turned dark orange brownafter one hour. Removal of the solvent left a solid residue which wasdissolved in 200 ml of ether and washed with 2×200 ml of water. Theethereal fraction was dried over magnesium sulfate and concentrated to aviscous oil. Silica gel column chromatography eluting with 9:1hexane-dichloromethane gave a white low melting solid which wasidentified as 2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane(Compound 5). The IR and NMR spectra were as follows:

IR (KBr): 3310 (strong, C.tbd.C--H), 2200 (weak, C.tbd.C).

NMR (CDCl₃) δ3.14 (s, 2H, C.tbd.C--H) and 6.90-7.85 ppm (distorted ABquartet, 16 H, aromatic).

EXAMPLE 2

This example illustrates the preparation of2,2-bis-[4-(4-ethynylphenylthio)phenyl]hexafluoropropane in accordancewith the present invention.

The preparation of2,2-bis[4-(4-ethynylphenylthio)phenyl]hexafluoropropane (11) is shownschematically in FIG. 2. An exemplary synthesis in accordance with theprocedure set forth in FIG. 2 is as follows.

A. Preparation of 2,2-Bis(4-mercaptophenyl)hexafluoropropane (Compound6)

Compound 6 and related bis(benzenethiol) compounds are disclosed inco-pending patent application Ser. No. 453,431, filed Dec. 27, 1982 andassigned to the same assignee as the present invention. Compound 6 andthe related compounds are prepared in a three-step process. In the firststep, a bisphenol is reacted with N,N-dimethylthiocarbamoyl chloride inthe presence of a base. Preferably, a 10% to 20% molar excess of thecarbamoyl chloride to bisphenol is used in this reaction. The preferredtemperature for the reaction is in the range of about 0° C. to about 60°C. at atmospheric pressure. The preferred time of reaction is in therange of about one to about two hours. From this first step of theprocess, a class of compounds called O-thiocarbamate esters is obtained.

In the second step of the process, the O-thiocarbamate esters from thefirst step are heated at a temperature in the range of about 150° C. toabout 275° C. for a period in the range of about one to about two hoursand at atmospheric pressure, preferably under an inert atmosphere suchas argon, to form a class of compounds called S-thiocarbamate esters.The rearrangement reaction is known by the general term "SmilesRearrangement".

In the third step of the process, the S-thiocarbamate esters from thesecond step are treated with a strong base such as potassium hydroxidein methanol, and then treated with a concentrated acid such ashydrochloric or nitric to form the desired bis(benzenethiol).

The following example illustrates the formation of the bis(benzenethiol)(Compound 6).

To a solution of 112 grams (0.33 mole) of Bisphenol AF[2,2-bis(4-hydroxyphenyl)hexafluoropropane]in 700 milliliters of benzenewas added 43.5 grams (0.66 mole) of 85% potassium hydroxide. Theresulting solution was refluxed with a trap to remove water; benzene wasthen removed at reduced pressure. To the resulting salt was added 700milliliters of dimethylformamide, the mixture was then cooled to 0° C.,and then 100 grams (0.81 mole) of N,N-dimethylthiocarbamyl chloride wasadded. The resulting mixture was heated to room temperature, then to 60°C., and maintained at 60° C. for one hour.

The product mixture was diluted with three liters of water and extractedtwice with an 80:20 benzene/hexane solution. The organic phase wasevaporated under reduced pressure to obtain a solid crystalline residue.The residue was recrystallized from a 5:1 methanol/ benezene solution toobtain 125 grams of a product melting at about 209°-211° C. This productwas the O-thiocarbamate ester of Bisphenol AF.

Fifteen grams (0.3 mole) of the O-thiocarbamate ester of bisphenol AFwas placed in a reaction vessel, and heated at 250° C. under argon forone hour. After cooling the product to room temperature, the glassyresidue was recrystallized from 60 milliliters of methanol to obtain 11grams of a product having a melting point of 141°-144° C. This productwas the S-thiocarbamate ester of the bisbenzenethiol derivative.

Seventy-five grams (0.15 mole) of the above S-thiocarbamate ester wasthen placed in 400 milliliters of methanol, and a solution of 75 gramsof potassium hydroxide in 200 milliliters of water was added. Thismixture was refluxed for one hour, cooled and diluted with two liters ofwater. A solution of 165 milliliters of concentrated HCl in one liter ofwater was then added. A precipitate was obtained which wasrecrystallized from a 3:1 methanol-water mixture to obtain 50 grams ofthe product 2,2-bis(4-mercaptophenyl)hexafluoropropane (Compound 6). Thedipotassium salt of Compound 6 was formed by reacting Compound 6 with apotassium-containing base.

B. Preparation of 2,2-Bis[4-(4-nitrophenylthio)phenyl]hexafluoropropane(Compound 7)

Compound 7 was synthesized by a nucleophilic aromatic substitutionreaction between the dipotassium salt of Compound 6 and 2 equivalents of4-chloronitrobenzene in dimethyl sulfoxide at 150°-160° C.

C. Preparation of 2,2-Bis[4-(4-aminophenylthio)phenyl]hexafluoropropane(Compound 8)

Compound 8 was is prepared by hydrogenating2,2-bis[4-(4-nitrophenylthio)phenyl]hexafluoropropane (Compound 7) in aParr apparatus under 4 atmospheres of hydrogen overpalladium-on-charcoal catalyst in ethyl alcohol solvent.

D. Preparation of 2,2-Bis[4-(4-iodophenylthio)phenyl]hexafluoropropane(Compound 9)

Compound 9 was prepared by treating Compound 8 with sodium nitritefollowed by potassium iodide according to the general diazotizationprocedure described in Example 1, Section A herein.

E Preparation of2,2-Bis[4-(4-trimethylsilylethynylphenylthio)phenyl]hexafluoropropane(Compound 10)

Compound 10 was prepared by treating Compound 9 with the palladiumcatalyst system and ethynyltrimethylsilane according to the generalprocedure described in Example 1, Section D herein.

F. Preparation of2,2-Bis[4-(4-ethynylphenylthio)phenyl]hexafluoropropane (Compound 11)

The final desired product2,2-bis[4-(4-ethynylphenylthio)phenyl]hexafluoropropane (Compound 11)was prepared by treating Compound 10 with anhydrousmethanoltetrahydrofuran and anhydrous potassium carbonate according tothe general procedure described in Example 1, Section E herein.

Compounds in accordance with the present invention may be utilized toform homopolymers or they may be copolymerized with various otherethynylated monomers such as acetylene-terminated sulfones (ATS) andacetyleneterminated imides. The amount of ethynylated monomersincorporated into the copolymer may be varied depending upon desiredproperties for the copolymer. Copolymers with from 1 to 99 weightpercent ethynylated monomers are possible.

In addition, the compounds may be used as plasticizing diluents in thepreparation of various high temperature resins such as polyimides,polybenzothiazoles, polyquinolines, and polyquinoxalines. When used as aplasticizing diluent, the compounds are preferably added to the resinsin amounts ranging from a few weight percent up to about 30 weightpercent. The amount of the present compounds added as a plasticizer canbe varied to achieve desired improvements during handling and processingof the resin along with desired reductions in brittleness of the finalresin product.

EXAMPLE 3

A homopolymer of 2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropanewas prepared by heating a sample of the neat material from 52° C. to315° C. in a button mold at the rate of 2°-3° C. per minute. Theresulting button was cured at 316° C. for 2 hours. The cured button hada glass transition temperature of approximately 333° C. The polymer wasstable, i.e. exhibited no weight loss during thermogravimetric analysisup to temperatures of above 500° C. The cured button was also post-curedfor a total of 24 hours at a temperature of 316° C. The resultingpost-cured button had a glass transition temperature of about 370° C.

EXAMPLE 4

A copolymer of 1 part of2,2-bis[4-(4-ethynylphenoxy)phenyl]hexafluoropropane and 4 parts of anacetylene-terminated polyimide oligomer of the type described in U.S.Pat. No. 4,438,273 at columns 9-10 with an average degree ofpolymerization (DP) of 15 was prepared by heating a sample of themixture in a button mold from 52° C. to 315° C. at the rate 2° C. perminute. The resulting button was cured at 316° C. for 24 hrs. The curedbutton had a glass transition temperature of approximately 325° C., andthermogravimetric analysis showed no weight loss up to 500° C.

Having thus described exemplary embodiments of the present invention, itshould be noted by those skilled in the art that the within disclosuresare exemplary only and that various other alternatives, adaptations andmodifications may be made within the scope of the present invention.Accordingly, the present invention is not limited to the specificembodiments as illustrated herein, but is only limited by the followingclaims.

What is claimed is:
 1. A diphenylhexafluoropropane compound having theformula: ##STR4## where R, R₁ and R₂ are hydrogen or ethynyl.
 2. Adiphenylhexafluoropropane compound according to claim 1 where R isethynyl and R₁ and R₂ are hydrogen.